OMRON CJ2 CPU Troubleshooting and Maintenance

2.3 Non fatal Error Handling

When there is a non fatal error, ERR/ALM flashes and the CPU continues to run. Common examples include:

Battery error (00F7): Low battery voltage or not installed. The battery (CJ1W-BAT01) needs to be replaced within 5 minutes, otherwise RAM data may be lost. It is recommended to power on for 5 minutes before turning off the power during replacement.

CPU bus unit error (0200~020F): Data exchange exception. Corresponding to a certain digit in A417 being ON, indicating the unit number. The unit can be restarted or replaced.

Special I/O unit error (0300~035F): Similar handling, refer to the specific unit manual.

Option board error (00D1): The option board was unplugged when powered on. Reconnect and restart the PLC.

2.4 Common problems with power supply units

Power unit faults often manifest as the POWER light not turning on. Check if the input voltage is within the allowable range (AC85~264V or DC19.2~28.8V) and if the wiring terminals are loose. CJ1W-PA205C has a replacement notification function. When the 7-segment code displays "0.0" and "A02" flashing alternately, the power unit should be replaced within 6 months.

CPU Unit Reset and Recovery Operations

3.1 Manually clearing errors

For non fatal errors or resettable fatal errors (such as E10, E11, etc.), they can be reset in the following three ways:

Press the ENT/RST key in front of the CPU (in monitoring or programming mode).

Connect the reset input terminals (terminals 13 and 14).

Send a reset command through communication (FLK model only).

3.2 Memory Clearing and Initialization

If E03 (EEPROM checksum error - set value) occurs, parameter initialization needs to be performed:

Press and hold the LVL key for 2 seconds to enter the initial setting level (SET indicator light is on).

Use the UP/DOWN keys to select parameter P28 (initialization setting value).

Press the ENT key to display "abt", press the UP key to change to "ini", and then press ENT to execute.

Power off and restart.

If E04 (total running time error) occurs, the total running time needs to be reset through P27, similar to the operation.

Maintenance and battery replacement

4.1 Key Points for Regular Inspection

It is recommended to conduct an inspection every 6 months to 1 year:

Environmental temperature (0~55 ℃), humidity (10%~90% without condensation)

Dust and corrosive gases

Are the connectors of each unit loose

Power supply voltage fluctuation

Battery life (approximately 5 years at 25 ℃)

4.2 Detailed steps for battery replacement

The CJ2 CPU unit uses lithium battery CJ1W-BAT01. Replacement process:

Ensure that the PLC has been powered on for at least 5 minutes (charging the capacitor).

Turn off the CPU unit (if you are concerned about static electricity, you can also replace it online, but you must touch the grounded metal to discharge).

Open the battery compartment cover in the upper left corner and carefully remove the old battery.

Install a new battery within 5 minutes (pay attention to aligning the protrusion with the groove: CJ2H on the upper right, CJ2M on the lower right).

Close the compartment lid and power on again. The battery error flag will be automatically cleared.

Warning: If the power is turned off for more than 5 minutes and the capacitor is not fully charged, I/O memory data in RAM may be lost. If the function of not saving data with the battery is used, the battery error detection can be turned off in the PLC settings.

Data backup and recovery operations

The CJ2 CPU unit supports two backup methods: simple backup (via memory card and DIP switch) and PLC backup tool (via CX Programmer).

5.1 Simple Backup Function (No Software Required)

Backup (CPU → memory card):

Insert formatted memory card (OMRON specified model: HMC-EF183/283/583).

Turn pin 7 of the DIP switch in front of the CPU to ON.

Press and hold the Memory Card Power Supply Switch for 3 seconds until the BUSY light is on, then release it.

Wait for the MCPWR light to flash once before turning off, and the BUSY light to turn off, indicating that the backup is complete.

Turn needle 7 back to OFF.

Recovery (memory card → CPU):

Power off and insert a memory card containing backup files.

Turn needle 7 to ON.

Power on, the system automatically recovers data from the memory card. The MCPWR light flashes once first, remains on during the recovery process, and turns off after completion.

Turn off the power, turn pin 7 back to OFF, and then turn it back on to run.

Comparison (memory card and CPU data): Pin 7 is OFF, press and hold the memory card power switch for 3 seconds. After the comparison is complete, the light will turn off to indicate consistency. If it flashes, it indicates inconsistency or error.

Note: Simple backup will backup user programs, parameter areas, I/O memory, symbol tables, annotations, and parameters of special I/O units and CPU bus units that support this function. After recovery, the CPU is in programming mode and needs to be manually switched to running mode.

5.2 PLC backup tool (via computer)

The PLC backup tool in CX Programmer allows for selective backup, comparison, and recovery of data. Especially suitable for situations where multiple devices need to be backed up or version managed.